The present invention is particularly useful in the automatic inspection of the "out-of-round" characteristics of glass containers. A radio frequency field is established in close proximity to a limited surface area of the container and the change in the field strength due to the position of a dielectric material in the field is measured. This measurement is preferably made by positioning a probe in the same plane as the field and centrally of the established field so that the field will pass through the air gap between the container or dielectric member being gauged and the front of the probe. The induced voltage at the probe will be an indication of the field strength due to the relative spacing of the probe and dielectric member.
It is desirable to segregate glass containers having predetermined deviations in the "out-of-round" dimension since such containers may exceed the acceptable physical size tolerances now being imposed by high speed filling, labelling and capping apparatus, and thereby create jam-ups or other undesirable down-time in the customer's plant.
The use of a high frequency field in automatic inspection has been the subject of recent patents assigned to the assignee of the present case, these patents being U.S. Pat. No. 3,379,306 issued Apr. 23, 1968; U.S. Pat. No. 3,393,799 issued July 23, 1968 and U.S. Pat. No. 3,708,064 issued Jan. 2, 1973. All of these references represent technology for inspecting dielectric members such as glass containers for deviations in the thickness of the walls of the glass. In all of these prior art devices, an inspection probe is very precisely positioned relative to its distance from the surface of the dielectric material or side wall of the glass container and is supported relative to the side wall of the container by a single roller, thus the probe is positioned relative to the bottle at a single point. The probe and roller are biased against the side wall of the rotating container. In this manner the spacing of the probe from the bottle is always constant throughout the measuring cycle.
The present invention, while utilizing the same type of high frequency probe, provides a system for mounting the probe and the positioning of the probe relative to the container such that the spacing of the probe from the container will change depending upon the roundness of the container or the deviations of the container wall from that of a right cylinder.
Accordingly, it is an object of this invention to provide an improved method and apparatus for inspecting glass containers for non-symmetricity.
It is a further object of this invention to provide an improved method and apparatus for inspecting dielectric members for out-of-round characteristics.
It is a still further object of this invention to segregate the bad or seriously irregular containers from the acceptable containers.